High-Performance FeP Catalyst for Electrochemical Ammonia Production and Recovery via Joule-Stripping

The electrochemical reduction of nitrate (NO₃RR) offers a promising route for decentralized and sustainable ammonia production while addressing environmental challenges associated with nitrate pollution. However, the development of practical implementations has been slowed by the challenge of creating highly stable and selective catalysts for strongly basic environments, along with the difficulty of efficiently recovering ammonia from dilute solutions. Here, we introduce a partially oxidized amorphous iron-phosphide (POA-FeP) electrocatalyst that combines high activity and stability with an innovative Joule-stripping strategy for ammonia recovery. Electrodeposited onto nickel foam (NF), the POA-FeP catalyst achieves benchmark partial current densities of -720 mA cm^-2 in neutral media and -932 mA cm^-2 in alkaline media, and near quantitative Faradaic efficiencies (FE). The robustness of the POA-FeP/NF catalyst was highlighted by its ability to maintain FE above 90% during continuous operation for over 1000 h at a total current density of -300 mA cm^-2. We demonstrate that the Joule heating resulting from the operation of the electrolyzer at high current density can be exploited to induce the volatilization of ammonia, which can then be recovered as solid ammonium chloride with >95% yield. This integrated Joule-stripping approach simplifies ammonia recovery and opens up new possibilities for scalable and energy-efficient nitrate reduction systems.